Process of making silver halide emulsions having polyvalent metal ions occluded therein

ABSTRACT

AN IMPROVED PROCESS IS DISCLOSED FOR PREPARING SILVER HALIDE EMULSIONS WHICH CONTAIN GRAINS HAVING POLYVALENT METAL IONS OCCLUDED THEREIN; THE IMPROVEMENT COMPRISES THE STEP OF FORMING THE SILVER HALIDE GRAINS IN THE PRESENCE OF (1) A PEPTIZER CONSISTING ESSENTIALLY OF AN ACRYLIC POLYMER AND (2) THE POLYVALENT METAL IONS TO BE OCCLUDED INSIDE THE GRAINS.

United States Patent @fice 3,690,888 PROCESS OF MAKING SILVER HALIDEEMUL- SIONS HAVING POLYVALENT METAL IONS OCCLUDED THEREIN Robert ElwinBacon, Ernest John Perry, and Evan Thomas Jones, Rochester, N.Y.,assignors to Eastman Kodak Company, Rochester, NY. No Drawing. FiledJune 4, 1970, Ser. No. 43,565 Int. Cl. G03c 1/02 U.S. Cl. 96-94 13Claims ABSTRACT F THE DISCLOSURE An improved process is disclosed forpreparing silver halide emulsions which contain grains having polyvalentmetal ions occluded therein; the improvement comprises the step offorming the silver halide grains in the presence of (1) a peptizerconsisting essentially of an acrylic polymer and (2) the polyvalentmetal ions to be occluded inside the grains.

This invention relates to methods of precipitating silver salts and theproducts produced thereby. In one aspect, this invention relates to thepreparation of silver halide crystals having polyvalent metal ionsoccluded therein wherein said silver halide crystals are formed in thepresence of a polymeric acrylic peptizer. In another aspect, thisinvention relates to a process wherein very low concentrations ofpolyvalent metal ions can be used during the precipitation of silversalt crystals in the presence of a linear addition acrylic peptizer.

It is known in the art to form silver halide crystals having polyvalentmetal ions occluded therein; emulsions of this type are generallydisclosed in US. Pats. 3,367,771 by Berriman; 2,717,833 by Wark;3,447,927 by Bacon; British Pat. 1,151,782 by Berriman; and French Pat.1,574,038 by Bacon. Prior-art techniques have generally involvedprecipitation of the silver halide in the presence of a gelatinousmedium, ripening the grains in a gelatinous medium or subsequentprecipitation in a gelatinous medium to achieve occluded polyvalentmetal ions within the silver salt crystal. Improved methods of forminggrains of this type are desirable to provide improved photographicproperties of the respective emulsions.

We have now found that improved silver salt compositions can be made byforming the silver halide grains in the presence of polyvalent metalions and a peptizer wherein said peptizer consists essentially of asynthetic, linear addition, acrylic polymer. Silver halide crystalsprepared by the present process are more regular in shape and moreuniform in size than crystals prepared under similar conditions in thepresence of gelatin. Moreover, foreign metal ion impurities aresubstantially reduced and apparently lower concentrations of the desiredpolyvalent metal ion can be used during the precipitation since it doesnot appear to be sequestered in the form of a complex with other ions orwith gelatin. Many other quasipeptizers such as, for example, polyvinylalcohol, do not exhibit the same improvements, which is apparently dueto relatively poor peptizing ability and the high contamination ofcatalysts, etc., during the polymerization reactions.

One preferred embodiment of this invention relates to precipitation ofsilver halide grains in the presence of 3,690,888 Patented Sept. 12,1972 polyvalent metal ions and a peptizer which consists essentially ofan acrylic polymer having groups appended thereto containing sulfideatoms and preferably thioether moieties wherein the sulfur atom inlinking two alkyl groups.

Another preferred embodiment relates to the precipitation of silverhalide crystals in the presence of trivalent metal ions and an acrylicpeptizer in an acidic medium.

Another highly preferred embodiment relates to the precipitation ofsilver halide crystals in the presence of bismuth, iridium, lead and/orosmium ions in an acrylic peptizer.

Still another preferred embodiment relates to improved silver halideemulsions wherein the silver halide grains are prepared in the presenceof trivalent metal ions and in an acrylic, polymeric silver halidepeptizer and wherein a direct-print-type halogen acceptor is contiguousto said silver halide grains.

Another embodiment relates to fogged, direct-positive silver halideemulsions wherein the fogged silver halide grains contain polyvalentmetal ions occluded therein and the grains are formed in the presence ofa peptizer which consists essentially of an acrylic polymer havinggroups appended thereto containing sulfide-sulfur atoms and preferablythioether moieties wherein the sulfur atom links two alkyl groups.

The synthetic linear addition polymers useful in this inventiongenerally include any good silver halide peptizer which can bepolymerized with a minimum of metal ion contaminant or wherein anycontaminants can be effectively removed after polymerization. Polymerswhich have been found to be very effective for this purpose are thoseacrylic copolymers which are also good silver halide peptizers. It isunderstood that acrylic means that the polymer contains units of theformula:

loan

where R is hydrogen or methyl, in the linear addition chain of thepolymeric material. In one embodiment, the preferred copolymers of thisinvention which can be used as peptizers contain a peptizer unit whichis derived from an amide or ester in which the respective amine oralcohol condensation residues comprise an organic radical having atleast one sulfide-sulfur atom linking two alkyl carbon atoms. Typicalpolymers of this type are disclosed in US. Ser. No. 701,084, filed Jan.29, 1968, now US. Pat. 3,615,624, such as, for example, peptizer unitsof acrylamides or acrylates containing an appended straight or branchedchain alkyl group, preferably appended to the ester or amide group, offrom about 2 to about 12 carbon atoms containing at least onesulfide-sulfur atom linking the respective alkyl carbon atoms in saidchain. Typical preferred peptizing moieties are units such as, forexample,

N- 3 -thiabutyl) acrylamide N- (3-thiapentyl) acrylamideN-(4-methyl-2-thiapentyl)acrylamide N-(2,5-dimethyl-4-thiahexyl)acrylamide N- S-thiaheptyl) acrylamide N-(4-thiaheptyl acrylamide N- (6-methyl-4-thiaheptyl acrylamide N-(3-thiaoctyl) acrylamide N- (7-thianonyl acrylamide N-6-ethyl-2-methyl-4-thiaoctyl) acrylamide N- 6-thia-2,4,9-trimethyldecyl)acrylamide N- 4-thiadodecyl acrylamide bis Z-thiabutyl) methyl acrylatemethylthioethyl acrylate methacryloylpyrolylmethionine methyl ester Thecopolymers used in this invention comprise at least and preferably atleast about 20% of units of the peptizing monomer, by weight, andpreferably units of at least one other ethylenically unsaturatedmonomer. Typical useful ethylenically unsaturated monomers includeacrylic acid; methacrylic acid; acrylic amines such asN,N-(dimethylacrylamide), 2-methyl-5-vinylpyridine, and the like;acrylic esters such as methyl acrylate, ethyl acrylate, methylmethacrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate,butyl acrylate, butyl methacrylate, 3-acryloxypropane-l-sulfonic acid,sodium salt, and the like. Preferably the ethylenically unsaturatedmonomers selected in making the peptizers used in this invention includemoieties which will form water-solubilizing units and hydrophobic units.

In another embodiment, the units of the peptizing monomers arecopolymerized with at least two other different monomers to provide abalanced polymer which can be coagulated and redispersed easily by merechange of pH. Typical polymers of this type are disclosed in Smith etal., U.S. Ser. No. 11,839, filed Feb. 16, 1970, entitled Terpolymers andTheir Use in Dispersions.

The copolymers of this invention can be generally polymerized bysolution polymerization, emulsion polymerization or bulk polymerizationprocedures, but they are preferably polymerized by solutionpolymerization procedures. The polymerization is carried out to obtain amolecular weight of the interpolymer of at least about 10,000 to about500,000, and preferably from about 30,000 to about 100,000. The inherentviscosities of the interpolymers generally range from about 0.05 toabout 4.

The procedure of this invention can generally be used to obtain improvedphotographic properties in any emulsion wherein the grains are preparedin such a manner to incorporate deliberately polyvalent metal ionstherein. Typical useful emulsions where the grains are formed in thepresence of a peptizing medium according to this invention and apolyvalent metal ion for occlusion therein include those described inU.S. Pats. 3,367,771 by Berriman; 2,717,833 by Wark; 3,447,927 by Bacon;and French Pat. 1,574,038 by Bacon.

In accordance with the invention, polyvalent metal ions are used in theprecipitation or formation of the silver halide grains. Divalent ionssuch as lead ions, tetravalent ions such as osmium, platinum, iridium,etc., and preferably trivalent metal ions are used in the process.Typical suitable trivalent metal ions include those of antimony,bismuth, arsenic, gold, iridium, rhodium and the like. The polyvalentmetal ion can be suitably added with the Water-soluble silver salt(e.g., sodium or potassium iodide, bromide or chloride) that isconventionally reacted to prepare or precipitate photographic silverhalide. Likewise, the polyvalent ions can be introduced into the silverhalide precipitation vessel with the peptizer. The polyvalent metal ionscan be added to the system as watersoluble inorganic salts, asorgano-metallic materials, as complexes, or as any other form ofmaterial that results in the availability of the respective polyvalentmetal ions during the formation of the silver halide. The amount ofpolyvalent metal utilized can be widely varied, although at least about1x10 and more generally l 10- to 2, mole percent based on the silverhalide is used. In one highly preferred embodiment, the grains areformed in the presence of lead, osmium, bismuth or iridium ions.

In preparing the silver halide used in the invention, the water-solublesilver salt and the water-soluble halide are reacted to precipitate thesilver halide, preferably under acidic conditions. The pH of the silverhalide precipitation is typically less than 6 and preferably less than5. Such acids or phosphoric, trifiuoracetic, hydrobromic, hydrochloric,sulfuric and nitric are typically utilized in the silver halideprecipitating media to maintain acidic conditions. The silver halidegrains useful in the invention generally have an average grain size ofabout .01 to 10 microns, and more generally about .05 to 2 microns, indiameter.

It is generally known in the art that changes in the halide ionconcentration during precipitation of the silver halide grains havingoccluded trivalent metal ions therein result in a more stable maximumdensity, especially when bismuth ions are occluded therein and thephotographic element containing said emulsion is exposed and processedby procedures as described in Colt, U.S. Pat. 3,418,122. Halide ionconcentration changes during the precipitation after incorporation ofpolyvalent metal ions in the grains also result in improved maximumdensity and other photographic properties when the present procedure isused to prepare the emulsion, especially when reactant concentrationssuch as pH and pAg are closely monitored and controlled by an automaticcontrol apparatus.

The invention can be further illustrated by the following examples.

EXAMPLE 1-A A control radiation-sensitive gelatino-silver chlorobromide(5 mole percent chloride and 95 mole percent bromide) photographicemulsion is prepared by slowly adding simultaneously an aqueous solutionof silver nitrate and an aqueous solution of alkali metal halides to anagitated aqueous acidic gelatin solution, which contains mg. of bismuthtrinitrate pentahydrate per silver mole.

EXAMPLE l-B A radiation-sensitive silver chlorobromide photographicemulsion is prepared according to the procedure of Example l-A. Thisemulsion differs only in the replacement of the gelatin peptizer with1/6 copoly[3-thiapentylacrylate-3-acryloxypropane 1 sulfonic acid,sodium salt]. Visual comparison of electron photomicrographs of thisemulsion as compared with the emulsion of Example l-A clearly shows thata more narrow grain size distribution is obtained in the emulsion ofExample l-B, i.e., a more monodispersed emulsion.

EXAMPLE 1-C Several photographic emulsions of the type described inExample l-A are prepared. These emulsions differ by the replacement ofthe gelatin peptizer with 1/2/5 (approximate by weight)copoly[3-thiapentylacrylate-acrylic acid-3-acryloxypropane-l-sulfonicacid, sodium salt] and varying the concentration of bismuth trinitratepentahydrate (such levels are given in the table of Example 2, labeledExamples 1-C(a) through 1C(e).

EXAMPLE 2 (PHOTOGRAPHIC DATA) The emulsions of Examples l-A and l-C aretreated with a dithiourazole-methyl vinyl ketone adduct as described inWise et al., U.S. Ser. No. 816,867 filed Apr. 4, 1969, now U.S. Pat.3,615,618. The emulsion of Example 1-B is treated with dithiourazolehydrazine salt. A gelatin solution, acting as the vehicle, is added toeach emulsion so as to have 5 percent by weight gelatin. Each sample isthen coated on a photographic paper support at about 60 mg. ofsilver/ftF.

Samples of each of these coatings are exposed 1 second on a Kodak RegentPrinter through a 0.15-density increment step wedge, then placed incontact with a heated platen at 235 C. for 5 seconds, and thenphotodeveloped for minutes with two 8-watt BL fluorescent lamps. Theresults are recorded in the following table:

6 We claim: 1. In a process for preparing silver halide emulsions 1 1:6copolylB-thiapentylacry1ate-3-acryloxypropane-l-sulfonic acid, sodiumsalt]. 5 1:2:5 (approximate) copoly[3-thiapentylacrylate'acrylicacid-3-acryloxypropane l-sulfonin acid, sodium salt].

Similar improved results are obtained when the emulsions are prepared inthe presence of a peptizer which consists essentially of the acryliccopolymers:

copoly(acryloylmethionine-acrylic acid) (3:1),

copoly(methylthioethyl acrylate-acrylic acid) (3.33:1),

copoly(acryloylmethionine methyl ester-acrylic acid-ethyl acrylate)(1.0:3.02:6.5) and copoly(N-(3,6 dithioctyl)acrylamide 3 aoryloyloxypropane-l-sulfonic acid, sodium salt) (1:15).

EXAMPLE 3 Fogged, direct-positive emulsions containing polyvalent metalions occluded in the grains have improved photographic properties whenthe grains are formed in the presence of an acrylic peptizer and thepolyvalent metal ion.

An internal sensitive emulsion is prepared by adding simultaneouslyaqueous solutions of silver nitrate and an alkali metal halide (97 .5mole percent potassium bromide and 2.5 mole percent potassium iodide) toa gelatin solution containing 100 mg. of potassium hexachloroiridate persilver mole.

A second internal-image emulsion is prepared similar to the proceduredescribed above except the gelatin peptizer is replaced withcopoly(3-thiapentylacrylate3- acryloxypropane-1-sulfonio acid sodiumsalt) (1:6 by weight).

The above washed emulsions are then fogged by adding 0.5 mg. of thioureadioxide per silver mole and 2.0 mg. of potassium chloroaurate per silvermole and heated for 60 minutes at 65 C. The emulsions are coated on afilm support at 100 mg. of silver/ft. exposed for 1 second on a Bauschand Lomb spectrograph and developed for 6 minutes in the followingsolvent developer:

G. l-phenyl-3-pyrazolidone 10 Sodium isoascorbate 40 Sodium sulfitePhenylmercaptotetrazole 0.25

It is apparent from the above data that a reversal image having asubstantially greater discrimination is obtained when the peptizer for asilver halide emulsion is an acrylic polymer.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention.

comprising preparing silver halide grains in the presence of a peptizer,said grains having polyvalent metal ions occluded therein, theimprovement comprising the step of forming the silver halide grains inthe presence of a peptizer which consists essentially of an acrylicpolymer; said polymer being a copolymer comprising at least onerecurring acrylic unit which has appended thereto by means of an amideor ester linkage an organic radical having at least one sulfide-sulfuratom linking two alkyl carbon atoms.

2. A process according to claim 1 wherein said polyvalent metal ions arepresent in a concentration of at least 1x10 mole percent based on thesilver halide.

3. A process according to claim 1 wherein said polyvalent metal ions aretrivalent metal ions.

4. A process according to claim 1 wherein said polyvalent metal ions arebismuth, osmium or iridium ions.

5. A process according to claim 1 wherein the polyvalent metal ions areoccluded in the silver halide grains in an acidic medium.

6. A process according to claim 1 wherein said acrylic polymer comprisesunits of an acrylamide or an acrylate containing appended organic groupscontaining from about 2 to about 12 carbon atoms and containing at leastone sulfide-sulfur atom linking 2 of said carbon atoms.

7. A process according to claim 1 wherein said peptizer iscopoly(N-(3-thiabutyl)acrylamide-3-acryloxypropane-l-sulfonic acid,sodium salt).

8. A process according to claim 1 wherein said peptizer iscopoly(3-thiapentylacrylate-acrylic acid -3-acryloxypropane-l-sulfonicacid, sodium salt).

9. A silver halide emulsion formed by the process of claim 1.

10. In a radiation-sensitive, silver halide emulsion comprising silverhalide grains formed in the presence of trivalent metal ions in anacidic medium and a halogen acceptor contiguous to said silver halidegrains, the improvement comprising the formation of said silver halidegrains in the presence of a silver halide peptizer consistingessentially of an acrylic polymer in addition to the formation of saidgrains in the presence of said polyvalent metal ions; said polymer beinga copolymer comprising at least one recurring acrylic unit which hasappended thereto by means of an amide or ester linkage an organicradical having at least one sulfide-sulfur atom linking two alkyl carbonatoms.

11. An improved silver halide emulsion according to claim 10 whereinsaid polyvalent metal ions are watersoluble.

12. An improved silver halide emulsion according to claim 10 whereinsaid polyvalent metal ions are bismuth 10I1S.

13. In a radiation-sensitive, direct-positive emulsion comprising foggedsilver halide grains having iridium ions occluded therein, theimprovement comprising the formation of said silver halide grains in thepresence of a silver halide peptizer consisting essentially of anacrylic polymer; said polymer being a copolymer comprising at least onerecurring acrylic unit'which has appended thereto 3,531,291 9/ 1970Bacon 96-94 by means of an amide or ester linkage an organic radical3,547,647 12/1970 Bacon 9694 having at least one sulfide-sulfur atomlinking two alkyl FOREIGN PATENTS carbon atoms.

References Cited 5 902,891 8/1962 Great Br tain. UNITED STATES PATENTS1,173,532 12/1969 Great'Bntaln 96114.7

3 419 39 2 9 3 Merrill 9 114 NORMAN TORCHIN, Pflmary Examlnef 3,457,0727/1969 Ditzer 9694 J. R. HIGHTOWER, Assistant Examiner 3,511,662 5/1970Jouy 96114 10 3,520,857 7/1970 Merrill 96-114 US. Cl. X.R.

3,531,289 9/1970 Wood 96--94 96-l14, 114.7

